Mineral oil base lubricant



2,925,386 MINERAL on; BASE LUBRICANT Wilhelm Dietrich, Hans-Joachim Mertens, and Fritz Wetter, Marl, Westphalia, Germany, assignors to ,Chemische Werke Huls Aktiengesellschaft, a corporation of o'Drawing. Application August 4, 1953" Serial No. 372,394

' Claims priority, application Germany August 25, 1952 2 Claims. (Cl. 252-475) It is known that in general mineral lubricating oils cannot be improved or can be only slightly improved with respect to their extreme pressure lubricating properties by the addition of aliphatic and aromaticnitro compounds including those which contain a halogen.

Mineral lubricating oils can however be improved with respect to extreme pressure lubricating properties by the addition of elemental sulfur. A greater resistance to loading at high pressure can be conferred upon gear and cutting oils by treating the corresponding mineral oils with sulfur. It has been proposed to add to mineral lubricating oil the sulfur containnig products obtained by treating fats and animal and vebetable oils with sulfur. Such sulfur-containing mineral oils are however often corrosive and their extreme pressure lubricating properties although somewhat improved are not up to present day requirements.

It has been found that mineral oil base lubricants which contain both organic nitro compounds and oil soluble dior poly-sulfides of xanthogenates hereinafter referred to as multi-sulfides of xanthogenates show adistinct improvement of their extreme pressure lubricating proper ties.

The expression lubricants having a mineral oil base includes not only true mineral oils but also the corresponding lubricant greases.

tenth) of theaddition of m lti-sulfide, of which latter,'de-

pending upon the extreme pressure lubricity required, amounts within the range from 0.5 to 10% by weight calculated upon the weight of the pure lubricant are used. The new lubricants, containing the nitro compounds and the multi-sulfides of xanthogenates, show no lossin' weight due to -corrosion; at normaltemperatures and only insignificant loss in weight due to corrosion at elevated, temperature and after along time of metals such as brass, bronze and copper. The lubricants which have been improved by the described additions of nitro and multi-sulfide compounds may be further improved by other well known additions for the improvement of extreme pressure lubricity, viscosity, solidification point, foaming resistance and resistance to oxidation.

Testing of the extreme pressure lubricating properties of mineral lubricating oils with additions of thelnitro and multi-sulfide compounds by the generally used four Suitable organic nitro compounds are for example,

m-dinitrobenzene, bromodinitrobenzene, chloronitrobenzene, B-dinitrophenol and their C-alkyl derivatives and mixtures thereof and other nitro compounds including nitroparaffines, nitronaphthalenes and nitronaphthols, this enumeration being merely illustrative, and not limitative.

The oil soluble multi-sulfides of xanthogenates are compounds of the general formula in which R stands for alkyl, cycloalkyl, aralkyl, aryl and.

heterocyclic groups which may be straight chain or branched or saturated or unsaturated and may contain metal atoms such as tin or zinc. X stands for'oxygen or sulfur and n means a figure from 0 to 5 or even The amount of nitrol compound and multi-sulfide of xanthogenate and the particular compound to be used depend upon the purpose for which the resulting lubricant is to be used. In general the addition of nitro'compound amounts toonly a small fraction (up to one ball apparatus (VKA) and method described in the publication 01 und Kohle, 1 944,.pages 19-23, shows that with additions of 0.1 to .25% of the organic nitro compounds together with from 1 to 2.5% of the multisulfides of xanthogenates permits the application of loads of from 400 to 1000 kg. before a welding or freezing of the balls occurs.

The invention is further described and illustrated in and by the following specific examples.

-. Example I A spindle oil having a VKA value of less than (density 15/4=0.9024, viscosity at 20 C.=8.40 E. and at 50 C. =2.47 E., viscosity index=ll5, solidify ing point=l7 C.) was not improved with respect to its extreme pressure lubricity by the addition of 0.25%

of dinitrophenol. By the addition of 2.5% of dibutylxanthic acid disulfide the VKA value was raised to 340. The addition of both 0.25% of dinitrophenol and 2.5 of the dibutylxanthic acid disulfide raised the VKA value to 440.

Example 2 To a mineral oil of average viscosity having a VKA value of 150 (density 15/4 0.78, viscosity at 20 C.= 47.2 E. and at 50 C. =8.49 E., viscosity index=104, solidifying point=-l2 C.) 2.5% of dibutylxanthic acid disulfide was added. The resulting lubricant had a VKA value of 480. By the further addition of 0.25% of fi-dinitrophenol the VKA 'value was increased to 950. The addition of 0.25% of the fl-dinitrophenol alone to the pure mineral oil did not produce any improvement of the extreme pressure lubricity.

Example 3 A lubricating oil, of a viscosity at 50 C.=20 E. and a VKA value of -180 shows after the addition of 2.5% dipropylxanthic acid disulfide a VKA value of 360, which raises after the addition of 0.15% 6-chloro- 2.4-dinitrophenol up to a value of440. The addition of 6-chloro-2.4-dinitrophenol alone to the pure lubricating oil did not produce any improvement of the lubricity.

The mixing of the said pure lubricating oil with 2% diethylxanthic acid tetrasulfide improves the VKA value of the oil up to 440460, by the further addition of 0.2% 2.4-dinitrophenol a lubricating'oil with the VKA value of 550-600 will be obtained.

The mixing of the said pure lubricating oil with 5% diethylhexylxanthic acid disulfide gives a lubricating oil with a VKA value of 500, which will be improved up to 600-650 by the further addition of 0.15 6-bromo2.4- dinitrophenol.

The multi-sulfides of a xanthogenate as well as the organic nitro compounds employed in the above examples may be substituted one with another in similar amounts and with similar results.

We claim:

1. A lubricant comprising a mineral oil base, 0.05-1% of an organic nitro compound selected from the group consisting of nitroparafiines, dinitrobenzenes dinitrophenols, nitronaphthalenes, nitronaphthols and their halogens and C-alkylderivatiyes, and 05-10% of an oil soluble multi-sulfide of a xanthogenate which is a member of the group of compounds of the general formula RX--CSS(S), S--CS--XR in which R is a member of the group consisting of alkyl,

'4 cyclo-alkyl, aralkyl and aryl, X is a member of the group consisting of sulfur and oxygen and n means a figure from 0 to 5, the ratio of said nitro compound to said oil soluble multi-sulfide being not more than 1 to 10.

2. A lubricant as defined in claim 1 in which the multi-sulfide of a xanthogenate is dibutylxanthic acid disulfide.

Downing et a1 Sept. 28, 1937 Mikeska et a1. ..7 July 29, 1941 

1. A LUBRICANT COMPRISING A MINERAL OIL BASE, 0.05-1% OF AN ORGANIC NITRO COMPOUND SELECTED FROM THE GROUP CONSISTING OF NITROPARAFFINES, DINITROBENZENES, DINITROPHENOLS, NITRONAPHTHALENES, NITROANAPHTHOLS AND THEIR HALOGENS AND C-ALKYLDERIVATIVES, AND 0.5-10% OF AN OIL SOLUBLE MULTI-SULFIDE OF A XANTHOGENATE WHICH IS A MEMBERBER OF THE GROUP OF COMPOUNDS OF THE GENERAL FORMULA 